The objectives of the coming year are: 1) to readminister tests of lung function to a cohort of residents of a defined geographic area in Los Angeles historically exposed to photochemical/oxidant pollutants, 2) to estimate the specificity and sensitivity of these field administered tests in identifying people who have or who will develop respiratory impairment and/or chronic obstructive respiratory disease, 3) to observe the rate of change in respiratory performance of this cohort in the five-year interval so that they may be compared to rates of change in cohorts in other areas of Los Angeles County exposed to different types and levels of pollutants which will be retested in subsequent years. All members of the original cohort will be located and retested. Probability samples of residents will be further field-tested in different periods of the year and restudied at UCLA. A panel of residents with reactive airways disease will be field-tested during high pollution episodes. Analytic techniques will be developed to assess longitudinal changes in respiratory function, measured by individual tests and groups of tests. Representativeness of pollutant levels recorded at fixed monitoring stations for the study area in which they are located will be investigated.